1. Field of the Invention
The present invention is generally directed to a depth sounder, such as employed in fish finding apparatus. More particularly, the present invention is directed to a depth sounder and method for eliminating noise.
2. Description of the Related Art
The use of sonar echo sounding for recreational and commercial fish finding purposes, and for other underwater object identification, is widespread. These devices utilize sonar signals to develop a view of underwater environment.
One major problem faced by manufacturers of depth sounders is that, underwater environments are often noisy and the noise levels can, and do, vary widely. This noise interferes with accurate underwater detection and makes it difficult, both for the device and the user, to interpret an underwater environment.
In order to alleviate the problem of noise, many prior depth sounder products utilize what is commonly known as a detection threshold, of a selected amplitude, such that sonar echo signals, which correspond to sonar pulses transmitted from the sounder device and which have reflected off of the bottom of a body of water or off of any object in the water, that are louder than the detection threshold are accepted, while sonar echo signals that are quieter than the detection threshold are rejected. More particularly, such products typically display, on a display screen, data corresponding to sonar echo signals which are louder than the detection threshold, but do not display data corresponding to sonar echo signals which are quieter than the detection threshold.
As will be appreciated, the placement of the detection threshold is a critical step in the manufacture of such depth sounders. In this regard, the higher the detection threshold value, the more noise that will be rejected and the more likely echo signals received by the depth sounder will be accurately interpreted as underwater environment. However, a high detection threshold has the drawback of potentially rejecting weak signals that, when compared with a lower detection threshold, would have been received and interpreted. Conversely, a low detection threshold allows weaker (and thus a potentially greater number of sonar echos) to be received and interpreted, but increases the likelihood that noise will be incorrectly interpreted as underwater environment.
While there are many theories and practices relating to the proper placement of the detection threshold, the need remains for a sonar depth sounder which efficiently adjusts the detection threshold based upon a change in noise levels. The present invention fills this need and other needs, in a unique manner.